The present invention relates to a chip photoelectric sensor assembly and a method for making the chip photoelectric sensor assembly.
As shown in FIG. 1, a chip photoelectric sensor assembly of the prior art has a photoelectric sensor chip 10 which is attached to a substrate 12 such that the chip 10 is electrically connected with the substrate 12 by a plurality of leads 14. The chip 10 is provided on the top thereof with a protective layer 16 which is made of a transparent resin material by molding.
Such a prior art chip photoelectric sensor as described above is defective in design in that the protective layer 16 is excessively thick and is apt to cause the refraction of light passing through the protective layer 16. Generally speaking, the optimal thickness of the protective layer 16 is about 50 microns.
As shown in FIG. 2, another prior art chip photoelectric sensor has a photoelectric sensor chip 21 which is provided on the top thereof with a protective layer 20, and in the underside thereof with a plurality of electrodes 22, with each having a projection 23 conductive to electricity. The chip 21 is further provided with a photoelectric sensor 24 and a transparent insulation layer 25 made of a resin material. The transparent insulation layer 25 is intended for use in mounting the chip 21 on an electrically-conductive layer 27 which is mounted on a glass substrate 26. This prior art chip photoelectric sensor assembly is susceptible to distortion which is brought about by the refraction of light passing through the glass substrate 26 and the transparent insulation layer 25.
The primary objective of the present invention is to provide a method for making a chip photoelectric sensor assembly which is free from the drawbacks of the prior art chip photoelectric sensor assemblies described above.
In keeping with the principle of the present invention, the foregoing objective of the present invention is attained by a chip photoelectric sensor assembly comprising a substrate, a printed circuit board mounted on the top of the substrate, a photoelectric sensor chip disposed on the top of the printed circuit board and provided on the top thereof with a photosensitive area which is formed by a plurality of photosensors, and a plurality of electric connection ports. The electric connection: ports are connected with the printed circuit board. The electrically-connected portion of the photoelectric sensor chip and the substrate is protected by an insulation layer. The photosensitive area of the photoelectric sensor chip is provided with a transparent protective layer of a hard coating material. In light of the transparent protective layer being very thin, the light refraction is averted.
The chip photoelectric sensor assembly is coated with a transparent layer of the hard coating material. A rigid transparent protective layer is formed only in the photosensitive area of the photoelectric sensor chip by the photolithographic process.